Field
The present invention relates to an apparatus and a method for transmitting power wirelessly.
Related Art
With the development of communication and information processing technology, the use of a smart terminal such as a smart phone, or the like has gradually increased and a charging scheme primarily applied to the smart terminal at present is a scheme in which an adapter connected to a power source is directly connected to the smart terminal to be charged by receiving external power or connected to the smart terminal through a USB terminal of a host to be charged by receiving USB power of the host.
In recent years, in order to reduce inconvenience that the smart terminal should be directly connected to the adapter or the host through a connection line, a wireless charging scheme in which a battery is wirelessly charged by using magnetic coupling without an electric contact has been gradually applied to the smart terminal.
There are several methods for supplying or receiving electric energy wirelessly, which representatively include an inductive coupling scheme based on an electromagnetic induction phenomenon and an electromagnetic resonance coupling scheme based on an electromagnetic resonance phenomenon by a wireless power signal of a specific frequency.
In both schemes, a communication channel is formed between a wireless charging apparatus and an electronic apparatus such as the smart terminal, which send and receive data to secure stability of power transmission and increase transmission efficiency and in the inductive coupling scheme, a power receiving apparatus moves during wirelessly transmitting the power, and as a result, the transmission efficiency may deteriorate and in the resonance coupling scheme, noise is generated in the communication channel, and as a result, a phenomenon may occur, in which the power transmission is stopped.
In the resonance coupling scheme, a time is further required for actualization and standardization is also slowly progressed, but in the inductive coupling scheme, standardization and commercialization of the technology are rapidly progressed.
In recent years, a foreign object detection (FOD) function to detect the power loss which occurs due to a foreign object laid between a transmitted and a receiver should be requisitely implemented in a product to which a wireless charging standard (WPC 1.1) of the inductive coupling scheme is applied. In a multi-coil type wireless charger, efficiency deteriorates in an overlapping area in which coils overlap with each other and the efficiency deterioration results in the power loss and the application of the FOD function, and as a result, coil switching frequently occurs.
Therefore, as a design purpose of the multi-coil type wireless charger, securing a charging area is difficult, which serves as a failure element in commercialization of a multi coil type product.